参考

使用 grep 提供行上下文控制（Context Line Control）参数，可以轻松实现上述目标。-A NUM, –after-context=NUM
Print NUM lines of trailing context after matching lines. Places a line containing a group separator (–) between contiguous groups of matches. With the -o or –only-matching option, this has no effect and a warning is given.

-B NUM, –before-context=NUM
Print NUM lines of leading context before matching lines. Places a line containing a group separator (–) between contiguous groups of matches. With the -o or –only-matching option, this has no effect and a warning is given.

-C NUM, -NUM, –context=NUM
Print NUM lines of output context. Places a line containing a group separator (–) between
contiguous groups of matches. With the -o or –only-matching option, this has no effect and a warning is given.